1. Field of the Invention
The present invention generally relates to testing multi-die packages and more particularly to isolating individual die in multi-die packages during testing.
2. Description of the Related Art
Integrated-circuit dice are typically subjected to a series of test procedures to ensure reliability. This can include electrical-characteristics testing, logic testing, and burn-in testing. In electrical-characteristics testing, a die can be tested for electrical parameters, such as input and output voltages, capacitances, and currents for the integrated circuits contained on the die. Logic tests are generally performed on a die that contains logic components, such as memory, state-machines, and the like. In logic testing, the die can be tested to measure its response to certain input stimulus. In burn-in testing, a die is typically overstressed. For example, the die can be subjected to higher than normal operating temperatures and voltages to verify its lifetime.
To perform these testing procedures, a die is typically mounted on a test/burn-in board. These boards form temporary connection with contacts on the packaged die. They also provide connections for a tester to provide test signals to the packaged die.
Over the years, multi-die packages that contain two or more dice have become increasing popular. More particularly, multi-die packages with a FLASH die have been in great demand for use in portable-electronic devices, such as cell phones, personal electronic devices, and the like.
In testing multi-die packages, it is desirable to test one die while other dice are isolated. In generally, this is achieved in part with test boards that are specifically configured for a particular set of dice in a multi-die package. As such, one board that is configured to test one set of dice in a multi-die package may not be used to test a different set of dice. Thus, when one die in a multi-die package is changed, a new test board may be required. This can be both cost and time prohibitive.
The present invention relates to testing a multi-die package. In accordance with one aspect of the present invention, the multi-die package includes a first die and a second die. The first die and the second die each have a VCC input. The second die also has a VCCIO input. The second die also includes at least one I/O pin connected to an I/O buffer having a driver and a pre-driver. In one embodiment of the present invention, the multi-die package is inserted/disposed in a test platform having a first and a second lead. The first lead is connected to the VCC input on the first die. The second lead is connected to the VCCIO input on the second die. The VCC input on the second die is connected to ground. The I/O pin of the second die is tri-stated using a control circuit disposed between the pre-driver and the driver of the I/O buffer.